I. Field of the Invention
This invention relates generally to carpentry tools, and more particularly to a device which may be readily attached to a standard carpenter's level to create a T-square useful for laying out patterns on plywood panels, gypsum board and similar materials.
II. Discussion of the Prior Art
A T-square is an instrument or tool commonly used by draftsmen and builders for drawing or scribing straight lines on panels, with the line extending perpendicular to a reference edge of that panel. It generally comprises an elongated rectangular blade to which is attached a head member where the head member includes a straight bottom edge which is displaced out of the plane of the rectangular blade with that bottom edge being oriented precisely at 90.degree. to the two side edges of the elongated rectangular blade.
In commercial and residential building, workmen often must lay out rectangular patterns on sheet material, such as wall board, plywood, wallpaper, etc. Such workmen will routinely have a carpenter's level as one of his/her tools. However, because of its shape, such workers will not routinely include a T-square in their tool boxes. While a carpenter's level along with a measuring tape can be used to lay out a pattern on sheet material, it is necessary when using that approach to measure in from a reference edge on the workpiece and mark a series of points and then use an edge of the carpenter's level to draw a series of straight line segments extending through the marks. This procedure is time consuming when contrasted to the use of a T-square for the same purpose. With a T-square, of course, it is only necessary to measure and mark at one point because the T-square itself will insure perpendicularity of the line being drawn through that single mark.
Accordingly, it would be helpful and convenient for a worker in the building trades to have a readily portable attachment for a carpenter's level that would convert the assembly into a T-square type tool. There is disclosed in the prior art the idea of attaching a separate head member to a carpenter's level to facilitate the squaring of corners when framing in doorways, windows and the like. In this regard, reference is made to the U.S. Pat. No. 2,761,215 to Macklanberg and the U.S. Pat. No. 4,910,876 to Channell. Neither of these devices, however, would be suitable as a T-square because neither provides a head attachment whose reference edge is offset from the plane of the level so as to allow the tool to cooperate with the edge of a sheetrock panel or the like to be marked and cut.
The U.S. Pat. No. 4,825,559 to Santos discloses a T-square type tool with a removable head, but the blade portion of the T-square is merely a flat ruler or scale and not a carpenter's level.